What city is colder, Boston or Chicago?

I'm curious to know which of these two cities is known for its colder climate. Is it Boston, with its proximity to the Atlantic Ocean and the New England region's notorious winters, or is it Chicago, which sits on the shores of Lake Michigan and is often associated with brutal Midwestern winters? Both of these cities experience significant snowfall and low temperatures during the colder months, so it's an interesting question to ponder. Which one of them do you think is colder?